linux-kernel - Re: [PATCH] CacheFiles: Fix error handling in cachefiles_determine_cache

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Message-Id: <20100512123629.41139fd5.akpm@linux-foundation.org>
Date:	Wed, 12 May 2010 12:36:29 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	David Howells <dhowells@...hat.com>
Cc:	torvalds@...ux-foundation.org, linux-cachefs@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] CacheFiles: Fix error handling in
 cachefiles_determine_cache_security()

On Wed, 12 May 2010 15:34:03 +0100
David Howells <dhowells@...hat.com> wrote:

> cachefiles_determine_cache_security() is expected to return with a security
> override in place.  However, if set_create_files_as() fails, we fail to do
> this.  In this case, we should just reinstate the security override that was
> set by the caller.
> 
> Furthermore, if set_create_files_as() fails, we should dispose of the new
> credentials we were in the process of creating.
> 
> Signed-off-by: David Howells <dhowells@...hat.com>
> ---
> 
>  fs/cachefiles/security.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/cachefiles/security.c b/fs/cachefiles/security.c
> index b5808cd..039b501 100644
> --- a/fs/cachefiles/security.c
> +++ b/fs/cachefiles/security.c
> @@ -77,6 +77,8 @@ static int cachefiles_check_cache_dir(struct cachefiles_cache *cache,
>  /*
>   * check the security details of the on-disk cache
>   * - must be called with security override in force
> + * - must return with a security override in force - even in the case of an
> + *   error
>   */
>  int cachefiles_determine_cache_security(struct cachefiles_cache *cache,
>  					struct dentry *root,
> @@ -99,6 +101,8 @@ int cachefiles_determine_cache_security(struct cachefiles_cache *cache,
>  	 * which create files */
>  	ret = set_create_files_as(new, root->d_inode);
>  	if (ret < 0) {
> +		abort_creds(new);
> +		cachefiles_begin_secure(cache, _saved_cred);
>  		_leave(" = %d [cfa]", ret);
>  		return ret;
>  	}

The changelog makes it hard for civilians to work out what the
user-visible effect of this bug was.

Should this fix be backported into -stable?
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